Methods for supplying a chemical within a subterranean formation

ABSTRACT

The method comprises deploying through a well a substantially longitudinal body comprising at least in part a degradable material able to release a chemical; positioning the longitudinal body at a downhole location from the well; and allowing the degradable material to degrade and the chemical to be released.

FIELD OF THE INVENTION

The invention generally relates to delivering chemicals downhole in awellbore. Certain types of chemicals are dissolved at a treatmentlocation or close to the treatment location.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

In the construction and development of wells formed in subterraneanformations, such as wells for the production of oil and gas, variousoperations are carried out that require the introduction of fluids ofdifferent types into the wellbore and/or into formation surrounding thewellbore.

Certain types of chemicals are preferentially mixed at a treatmentlocation or close to the treatment location. For example, certain mixedchemicals produce strong acids or have highly viscous reaction products,and it may be desirable to minimize equipment contact with the mixedchemicals, or to minimize the operational complexity of mixing anddelivering the chemicals. Presently available methods for deliveringchemicals directly to a downhole location have drawbacks, including therequirement to prepare for the chemical delivery with special equipmentor procedures before the chemical delivery is needed, difficulty inensuring that the chemicals are delivered to a desired depth, anddifficulty in ensuring the chemicals mix at the desired depth.Therefore, further technological developments are desirable in thisarea.

SUMMARY

In a first aspect, a method comprises deploying through a well asubstantially longitudinal body comprising at least in part a degradablematerial able to release a chemical; positioning the longitudinal bodyat a downhole location from the well; and allowing the degradablematerial to degrade and the chemical to be released.

In a second aspect, a method comprises deploying with a slicklinethrough a well a substantially longitudinal body attached to theslickline, wherein the longitudinal body comprises at least in part adegradable material able to release a chemical; positioning with theslickline the longitudinal body at a downhole location from the well;and allowing the degradable material to degrade and the chemical to bereleased.

In a third aspect, a method comprises adding to a tool selected from thegroup consisting of slickline, wireline, coil-tubing, micro-coil tubing,and drill string, a substantially longitudinal body comprising at leastin part a degradable material; deploying the tool through a well;positioning with the tool the longitudinal body at a downhole locationof the well; and allowing the degradable material to degrade and thechemical to be released.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an illustration of two embodiments for delivering achemical to a downhole location in a wellbore.

DETAILED DESCRIPTION

At the outset, it should be noted that in the development of any actualembodiments, numerous implementation-specific decisions must be made toachieve the developer's specific goals, such as compliance with systemand business related constraints, which can vary from one implementationto another. Moreover, it will be appreciated that such a developmenteffort might be complex and time consuming but would nevertheless be aroutine undertaking for those of ordinary skill in the art having thebenefit of this disclosure.

The description and examples are presented solely for the purpose ofillustrating embodiments of the invention and should not be construed asa limitation to the scope and applicability of the invention. In thesummary of the invention and this detailed description, each numericalvalue should be read once as modified by the term “about” (unlessalready expressly so modified), and then read again as not so modifiedunless otherwise indicated in context. Also, in the summary of theinvention and this detailed description, it should be understood that aconcentration range listed or described as being useful, suitable, orthe like, is intended that any and every concentration within the range,including the end points, is to be considered as having been stated. Forexample, “a range of from 1 to 10” is to be read as indicating each andevery possible number along the continuum between about 1 and about 10.Thus, even if specific data points within the range, or even no datapoints within the range, are explicitly identified or refer to only afew specific, it is to be understood that inventors appreciate andunderstand that any and all data points within the range are to beconsidered to have been specified, and that inventors possession of theentire range and all points within the range disclosed and enabled theentire range and all points within the range.

According to a first embodiment and referring to FIG. 1A, a system 100includes a substantially longitudinal body comprising at least in part adegradable material 101 able to release a chemical. In anotherembodiment, the system 100 comprises a second degradable material 102able to release second chemical.

According to a second embodiment and referring to FIG. 1B, the system100 includes a slickline or wireline 103 and a substantiallylongitudinal body attached to the slickline, wherein the longitudinalbody comprises at least in part a degradable material 101 able torelease a chemical. In another embodiment, the system 100 comprises asecond degradable material 102 able to release a second chemical. In oneembodiment, the degradable material 101 or the second degradablematerial 102 may comprise a degradable single or a degradable multicoreor a degradable hollow core containing a chemical or a reactive fluid.

According to one embodiment, the first chemical may be used to help torelease the second chemical or according to a second embodiment, thefirst and second chemicals are released independently. According to somefurther embodiments, the system 100 may comprise a third, fourth orseveral degradable materials able to release respectively, a third,fourth or several chemicals. The release mechanism can be done bycascade (one chemical helping to release another chemical) orindependently each other or a combination of both. The degradablematerials may be the same or different, releasing different chemicals orthe degradable materials may the different, releasing same chemical.

According to some embodiments, the system may be embodied as a systemmade entirely of degradable material. In one example represented in FIG.1, the system is characterized by helicoidal wires made of degradablematerials.

The degradable material is made of a soluble substrate where thechemical is formed or trapped with the soluble substrate. Underspecified conditions including time, temperature, pH values, and/or inthe presence of certain solvents (e.g. and without limitation—water,oil, gas, xylene, acetone, or any other solvent understood in the art)the soluble substrate dissolves partially or completely, exposing orreleasing the chemical to the surrounding fluid. In certain embodiments,the soluble substrate dissolves over a period of time in the fluidsalready present (or planned to be present) in the wellbore (e.g. thedrilling fluid, hydraulic fracture treatment fluid, gravel packtreatment fluid, etc.), and the release fluid is therefore the fluidalready present in the wellbore. According to some embodiments, thedegradable material degrades with the help of a release fluid. Therelease fluid can be any type of chemistry and can be naturally presentdownhole or can be injected downhole in another step. Examples ofrelease fluid are solvents cited previously.

Examples of degradable material are material made of degradable fibersor degradable polymers. The differing molecular structures of thedegradable materials that are suitable give a wide range ofpossibilities regarding regulating the degradation rate of thedegradable material. The degradability of a polymer depends at least inpart on its backbone structure. One of the more common structuralcharacteristics is the presence of hydrolyzable and/or oxidizablelinkages in the backbone. The rates of degradation of, for example,polyesters, are dependent on the type of repeat unit, composition,sequence, length, molecular geometry, molecular weight, morphology(e.g., crystallinity, size of spherulites, and orientation),hydrophilicity, surface area, and additives. Also, the environment towhich the polymer is subjected may affect how the polymer degrades,e.g., temperature, presence of moisture, oxygen, microorganisms,enzymes, fluid flow past the polymer, pH, and the like. One of ordinaryskill in the art, with the benefit of this disclosure, will be able todetermine what the optimum polymer would be for a given applicationconsidering the characteristics of the polymer utilized and theenvironment to which it will be subjected.

Suitable examples of polymers that may be used include, but are notlimited to, homopolymers, random aliphatic polyester copolymers, blockaliphatic polyester copolymers, star aliphatic polyester copolymers, orhyperbranched aliphatic polyester copolymers. Such suitable polymers maybe prepared by polycondensation reactions, ring-opening polymerizations,free radical polymerizations, anionic polymerizations, carbocationicpolymerizations, coordinative ring-opening polymerization for, such as,lactones, and any other suitable process. Specific examples of suitablepolymers include polysaccharides such as dextran or cellulose; chitins;chitosans; proteins; aliphatic polyesters; poly(lactides);poly(glycolides); poly(ε-caprolactones); poly(hydroxy ester ethers);poly(hydroxybutyrates); polyanhydrides; polycarbonates;poly(orthoesters); poly(acetals); poly(acrylates); poly(alkylacrylates);poly(amino acids); poly(ethylene oxide); poly ether esters; polyesteramides; polyamides; polyphosphazenes; and copolymers or blends thereof.Other degradable polymers that are subject to hydrolytic degradationalso may be suitable. Of these suitable polymers, aliphatic polyestersare preferred. Of the suitable aliphatic polyesters, polyesters of α orβ hydroxy acids are preferred. Poly(lactide) is most preferred.Poly(lactide) is synthesized either from lactic acid by a condensationreaction or more commonly by ring-opening polymerization of cycliclactide monomer. The lactide monomer exists generally in three differentforms: two stereoisomers L-and D-lactide; and D, L-lactide(meso-lactide). The chirality of the lactide units provides a means toadjust, inter alia, degradation rates, as well as the physical andmechanical properties after the lactide is polymerized. Poly(L-lactide),for instance, is a semicrystalline polymer with a relatively slowhydrolysis rate. This could be desirable in applications where slowdegradation of the degradable material is desired. Poly(D,L-lactide) isan amorphous polymer with a much faster hydrolysis rate. Thestereoisomers of lactic acid may be used individually or combined foruse in the compositions and methods of the present invention.Additionally, they may be copolymerized with, for example, glycolide orother monomers like ε-caprolactone, 1,5-dioxepan-2-one, trimethylenecarbonate, or other suitable monomers to obtain polymers with differentproperties or degradation times. Additionally, the lactic acidstereoisomers can be modified by blending high and low molecular weightpolylactide or by blending polylactide with other aliphatic polyesters.For example, the degradation rate of polylactic acid may be affected byblending, for example, high and low molecular weight polylactides;mixtures of polylactide and lactide monomer; or by blending polylactidewith other aliphatic polyesters.

One guideline for choosing which composite particles to use in aparticular application is what degradation products will result. Anotherguideline is the conditions surrounding a particular application. Inchoosing the appropriate degradable material, one should consider thedegradation products that will result. For instance, some may form anacid upon degradation, and the presence of the acid may be undesirable;others may form degradation products that would be insoluble, and thesemay be undesirable. Moreover, these degradation products should notadversely affect other operations or components.

The physical properties of degradable polymers may depend on severalfactors such as the composition of the repeat units, flexibility of thechain, presence of polar groups, molecular mass, degree of branching,crystallinity, orientation, etc. For example, short chain branchesreduce the degree of crystallinity of polymers while long chain brancheslower the melt viscosity and impart, inter alia, extensional viscositywith tension-stiffening behavior. The properties of the materialutilized can be further tailored by blending, and copolymerizing it withanother polymer, or by a change in the macromolecular architecture(e.g., hyper-branched polymers, star-shaped, or dendrimers, etc.). Theproperties of any such suitable degradable polymers (such ashydrophilicity, rate of biodegration, etc.) can be tailored byintroducing functional groups along the polymer chains. One of ordinaryskill in the art, with the benefit of this disclosure, will be able todetermine the appropriate functional groups to introduce to the polymerchains to achieve the desired effect.

The above mentioned degradable materials in one embodiment are comprisedsolely of polyester particles, e.g., the system can be free oressentially free of non-polyester solids. In another embodiment, thepolyester can be mixed or blended with other degradable or dissolvablesolids, for example, solids that react with the hydrolysis products,such as magnesium hydroxide, magnesium carbonate, dolomite (magnesiumcalcium carbonate), calcium carbonate, aluminum hydroxide, calciumoxalate, calcium phosphate, aluminum metaphosphate, sodium zincpotassium polyphosphate glass, and sodium calcium magnesiumpolyphosphate glass, for the purpose of increasing the rate ofdissolution and hydrolysis of the degradable material, or for thepurpose of providing a supplemental bridging agent that is dissolved bythe hydrolysis products. Moreover, examples of reactive solids that canbe mixed include ground quartz (or silica flour), oil soluble resins,degradable rock salts, clays such as kaolinite, illite, chlorite,bentonite, or montmorillonite, zeolites such as chabazite,clinoptilolite, heulandite, or any synthetically available zeolite, ormixtures thereof. Degradable materials can also include waxes, oilsoluble resins, and other materials that degrade or become soluble whencontacted with hydrocarbons.

The chemical may be any chemical that is desired to be delivered at adownhole location, and may include a polymer cross-linker, a breaker, anacid or an acid precursor, a polyacrylamide, a chemical that contributesto the formation of (or that forms) a fluid loss pill in the surroundingfluid when released, an encapsulated chemical, and/or a coated chemical.Other non-limiting examples of the chemical include sodium hydroxide,fumaric acid, a granular acid, a borate cross-linker, and/or a zirconiumcross-linker. The chemical may be in a solid state and, upon release tothe surrounding fluid, the chemical may go into solution, become a gas,and/or remain solid. In certain embodiments, the chemical may be foundwithin solid particles in a liquid state, a gas state, and/or anadsorbed material within the solid particles. In certain embodiments,the degradable material when subject to a chemical reaction or aphysical transformation may become the chemical. For example, when solidaluminum as degradable material is used, action of acid may releasealuminum ions which are the chemicals.

In one example, the degradable material is aluminum. An aluminum wire orline is used to release aluminum ions downhole. The wire is transformedinto soluble aluminum ions by lowering the end of the wire into asolution containing an acid such as hydrochloric acid, hydrofluoricacid, phosphoric acid, or nitric acid. Additional aluminum can bedissolved by feeding the line into the well at the same rate as itdissolves downhole. The aluminum ions act as crosslinking agents andmight be needed to effect a crosslink of the solution existing downhole.According to some embodiments, the solution may be a viscosifying agent,for example a polysaccharide such as substituted galactomannans, such asguar gums, high-molecular weight polysaccharides composed of mannose andgalactose sugars, or guar derivatives such as hydroxypropyl guar (HPG),carboxymethylhydroxypropyl guar (CMHPG) and carboxymethyl guar (CMG),hydrophobically modified guars, guar-containing compounds. Also, theviscosifying agent may be a synthetic polymer such as polyvinylpolymers, polymethacrylamides, cellulose ethers, lignosulfonates, andammonium, alkali metal, and alkaline earth salts thereof. More specificexamples of other typical water soluble polymers are acrylicacid-acrylamide copolymers, acrylic acid-methacrylamide copolymers,polyacrylamides, partially hydrolyzed polyacrylamides, partiallyhydrolyzed polymethacrylamides, polyvinyl alcohol, polyalkyleneoxides,other galactomannans, heteropolysaccharides obtained by the fermentationof starch-derived sugar and ammonium and alkali metal salts thereof.Also, the viscosifying agent may be a cellulose derivative such ashydroxyethylcellulose (HEC) or hydroxypropylcellulose (HPC),carboxymethylhydroxyethylcellulose (CMHEC) and carboxymethycellulose(CMC). Also, the viscosifying agent may be a biopolymer such as xanthan,diutan, and scleroglucan.

According to further embodiments, other metal ions can be used ascrosslinking agents. Therefore the degradable material may be magnesium,borate, titanium, zirconium, chromium, and antimony, and compositionscontaining these compounds.

In another example, the degradable material is a composite material. Aline which is made from a composite material is used. The compositematerial includes a chemical contained within a strong matrix such asplastic. The addition of a solvent downhole will release the chemicalfrom the composite. According to further embodiments, a concentric wireof dissimilar degradable materials that can deploy different chemistriesmay be used. The inner material being released after the outer materialhas been degraded.

Still in another example, the degradable material is soluble at a pHthat is significantly different than a treating fluid, and the wellboreis treated with the treating fluid. In the example, where it is desiredthat the chemical be delivered, the release fluid may be delivered as aslug of treatment fluid having the pH to dissolve the degradablematerial. In a further example, the chemical may comprise a chemicaldelivered at the end of a fracture treatment (non-limiting examples oftreatment chemicals include a sand control resin, amine based curingagents, fibers (having a chemical composition) that reduce proppantflowback, or a high concentration breaker), and when conditionsconsistent with delivering the treatment chemical occur (e.g. animminent screen-out, the end of the treatment, etc.) then a slug oftreatment fluid is delivered to release the chemical.

In certain embodiments, the release fluid includes a solvent thatdissolves the degradable material. In certain embodiments, the releasefluid includes a lowered pH, an elevated pH, a solvent, and/or anabrasive. The composition of the release fluid may be variable,according to whether the release fluid is removing or degrading thedegradable material.

Still in another example, the degradable material is a string ofpoly(lactide) acid (PLA); poly(glycolide) acid (PGA) or a combination ofthe two that in itself hydrolyzes and generates acid/pH at a specificlocation and triggers specific chemistry release. A pleated wire/stringmade of e.g. PLA and PGA that can be temperature triggered may also berealized. PGA for temperature below 225F applications and later triggerPLA at a higher temperature to generate acid.

In another embodiment, an electrical conductive wire may be used aroundwhich PGA and/or PLA wires are wrapped. The conductive wire may be usedto generate heat and activate PGA or PLA wires to generate acid if thebottomhole temperature is lower than the natural decompositiontemperature for the PLA or PGA.

A technique for chemical deliver downhole is described. The techniqueincludes an operation to deploy a substantially longitudinal bodyincluding a chemical. The technique includes an operation to positionthe longitudinal body at a downhole location of a well. And thetechnique includes allowing the chemical to be released. Optionally arelease fluid can be used. An operation to flow the release fluid nearthe longitudinal body may be performed, thereby releasing at least aportion of the chemical into the release fluid.

In certain embodiments, the operation to release the chemical includesan operation to dissolve the chemical into the release fluid and/or todegrade a degradable material to expose the chemical, and/or a substratesupporting the chemical, to the release fluid. In certain embodiments,the chemical when released will have an exothermic reaction with thesecond fluid and control the kinetics. The operation to degrade adegradable material includes varying a pH value of the release fluidwhere the degradable material is responsive to the pH value, includingan abrasive material in the release fluid that removes at least part ofthe degradable material, and/or providing a release fluid wherein thedegradable material is soluble in the release fluid. The operationsutilizing the release fluid may include utilizing varying release fluidsin multiple steps or stages, including varying pH values, varyingtemperature values, and/or varying compositions of the release fluid. Inone example, an activator that removes the degradable material isincluded in a part of the release fluid, and the remaining release fluiddissolves the exposed chemical.

In certain embodiments, the technique includes an operation to provideat least part of the chemical as an encapsulated chemical, and anoperation to release the encapsulated chemical into a formation fluidlycoupled to the wellbore. In certain embodiments, the technique furtherincludes an operation to form a second degradable material having asecond chemical, where the chemical releases in response to a firstrelease operation, and where the second chemical releases in response toa second release operation. In certain embodiments, the techniquefurther includes an operation to form a second degradable materialhaving a second chemical, where the chemical releases in response to afirst release operation, and where the second chemical releases inresponse to the release of said first chemical (cascade mechanism). Forexample, temperature could be a first operation trigger that releasesacid from PLA degradable material. The acid then dissolves aluminumdegradable material which release aluminum ions. Or the acid could begindissolving the wall of an encapsulated second material and allow it towork, such as a breaker. The technique further includes an operation toselectively release the chemical or the second chemical by performingthe first release operation or the second release operation. Thetechnique further includes an operation to attach the longitudinal bodyto a slickline, a wireline, a coiled tubing or a micro-coil tubing, andto deliver the longitudinal body to a specified depth with the tool.According to certain embodiments, the longitudinal body may be attachedto the line with a connector able to release the longitudinal body. Theconnector may release the longitudinal body through an actuator whichmay respond to a chemical reaction, a mechanical trigger or physicaltrigger. The chemical reaction may be triggered by the treating fluid.

According to certain embodiments, the line may include adapters forweight bars to assist in its deployment to the desired depth in thewellbore.

Certain embodiments of the method include one or more of the operationsdescribed following. Operations described may be substituted, replaced,re-ordered, divided, and/or grouped in various embodiments.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof and it can be readily appreciatedby those skilled in the art that various changes in the size, shape andmaterials, as well as in the details of the illustrated construction orcombinations of the elements described herein can be made withoutdeparting from the spirit of the invention.

1. A method comprising: (a) deploying through a well a substantiallylongitudinal body comprising at least in part a degradable material ableto release a chemical; (b) positioning the longitudinal body at adownhole location from the well; and (c) allowing the degradablematerial to degrade and the chemical to be released.
 2. The method ofclaim 1, wherein the longitudinal body is positioned on a tool selectedfrom the group consisting of slickline, wireline, coil-tubing,micro-coil tubing, drill string, and combination thereof.
 3. The methodof claim 1, wherein the degradable material is degraded at the downholelocation with addition of a release fluid, which is naturally present atdownhole location or injected.
 4. The method of claim 3, wherein thedegradable material is degraded at the downhole location with a trigger.5. The method of claim 5, wherein the trigger is selected from the groupconsisting of: temperature, mechanical wave including acoustic wave, andelectromagnetic wave (microwave, UV).
 6. The method of claim 1, whereinthe longitudinal body further comprises at least in part a seconddegradable material able to release a second chemical.
 7. The method ofclaim 6, wherein the chemical or the second chemical is selected fromthe group consisting of: polymer cross-linker, a breaker, an acid or anacid precursor, a polyacrylamide and mixtures thereof.
 8. The method ofclaim 6, wherein the degradable material or the second degradablematerial is selected from the group consisting of: lactide, glycolide,polylactic acid, polyglycolic acid, copolymers of polylactic acid andpolyglycolic acid, copolymers of glycolic acid with other hydroxy-,carboxylic acid-, or hydroxycarboxylic acid-containing moieties,copolymers of lactic acid with other hydroxy-, carboxylic acid-, orhydroxycarboxylic acid-containing moieties, and mixtures thereof.
 9. Amethod comprising: (a) deploying with a slickline through a well asubstantially longitudinal cylindrical body attached to the slickline,wherein the longitudinal body comprises at least in part a degradablematerial able to release a chemical; (b) positioning with the slicklinethe longitudinal body at a downhole location from the well; and (c)allowing the degradable material to degrade and the chemical to bereleased.
 10. The method of claim 9, wherein the degradable material isdegraded at the downhole location with addition of a release fluid,which is naturally present at downhole location or injected.
 11. Themethod of claim 9, wherein the degradable material is degraded at thedownhole location with a trigger.
 12. The method of claim 11, whereinthe trigger is selected from the group consisting of: temperature,mechanical wave including acoustic wave, and electromagnetic wave(microwave, UV).
 13. The method of claim 9, wherein the longitudinalbody further comprises at least in part a second degradable materialable to release a second chemical.
 14. The method of claim 13, whereinthe chemical or the second chemical is selected from the groupconsisting of: polymer cross-linker, a breaker, an acid or an acidprecursor, a polyacrylamide and mixtures thereof.
 15. The method ofclaim 13, wherein the degradable material or the second degradablematerial is selected from the group consisting of: lactide, glycolide,polylactic acid, polyglycolic acid, copolymers of polylactic acid andpolyglycolic acid, copolymers of glycolic acid with other hydroxy-,carboxylic acid-, or hydroxycarboxylic acid-containing moieties,copolymers of lactic acid with other hydroxy-, carboxylic acid-, orhydroxycarboxylic acid-containing moieties, and mixtures thereof.
 16. Amethod comprising: (a) adding to a tool selected from the groupconsisting of slickline, wireline, coil-tubing, micro-coil tubing, anddrill string, a substantially longitudinal body comprising at least inpart a degradable material; (b) deploying the tool through a well; (c)positioning with the tool the longitudinal body at a downhole locationof the well; and (d) allowing the degradable material to degrade and thechemical to be released.
 17. The method of claim 16, wherein thechemical is selected from the group consisting of: polymer cross-linker,a breaker, an acid or an acid precursor, a polyacrylamide and mixturesthereof.
 18. The method of claim 16, wherein the degradable material isselected from the group consisting of: lactide, glycolide, polylacticacid, polyglycolic acid, copolymers of polylactic acid and polyglycolicacid, copolymers of glycolic acid with other hydroxy-, carboxylic acid-,or hydroxycarboxylic acid-containing moieties, copolymers of lactic acidwith other hydroxy-, carboxylic acid-, or hydroxycarboxylicacid-containing moieties, and mixtures thereof.
 19. The method of claim16, wherein the degradable material is degraded at the downhole locationwith addition of a release fluid, which is naturally present at downholelocation or injected.
 20. The method of claim 16, wherein the degradablematerial is degraded at the downhole location with a trigger.
 21. Themethod of claim 20, wherein the trigger is selected from the groupconsisting of: temperature, mechanical wave including acoustic wave, andelectromagnetic wave (microwave, UV).